CVE-2026-97984
Description
A flaw was found in the Linux kernel's IPv6 networking subsystem. A local user could cause a Denial of Service (DoS) by exploiting an integer overflow in the User Datagram Protocol (UDP) length calculation. When Path MTU Discovery is enabled on a network device configured with an unusually large Maximum Transmission Unit (MTU), transmitting oversized UDP packets can exceed the 16-bit length limit and trigger an internal kernel warning.
Statement
A low impact flaw was found in the Linux kernel IPv6 networking subsystem. A local unprivileged user on Red Hat Enterprise Linux 10 or Red Hat In-Vehicle OS 2 could cause a denial of service by opening an IPv6 UDP socket, setting IPV6_MTU_DISCOVER to IPV6_PMTUDISC_DO or IPV6_PMTUDISC_PROBE, and sending an oversized UDP packet over a network device configured with an MTU larger than IP6_MAX_MTU (65535 bytes). Under those conditions the computed UDP length of 65536 overflows the 16-bit length field and triggers a kernel WARN in udp_set_len_short, resulting in failed packet transmission; on systems where panic_on_warn is enabled, this warning escalates to a kernel panic. Red Hat Enterprise Linux 7, 8, and 9, and the OpenShift Container Platform RHEL CoreOS images, are not affected because the vulnerable code is not present in those releases. Red Hat rates this flaw low impact: although the CVSS:3.1 base score is 5.5 (Moderate), exploitation requires local access together with the uncommon configuration of a device MTU above 65535 bytes, and the consequence is limited to a warning and packet failure rather than memory corruption or privilege escalation. Because of this low impact and the impractical preconditions, the fix has been deferred to a future update of the affected releases; the residual risk is a local denial of service confined to systems using such large-MTU network devices.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 5.5 | N/A | N/A |
| Attack Vector | Local | N/A | N/A |
| Attack Complexity | Low | N/A | N/A |
| Privileges Required | Low | N/A | N/A |
| User Interaction | None | N/A | N/A |
| Scope | Unchanged | N/A | N/A |
| Confidentiality | None | N/A | N/A |
| Integrity Impact | None | N/A | N/A |
| Availability Impact | High | N/A | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (Memory); DoS: Instability
This weakness can generally lead to undefined behavior and therefore crashes. When the calculated result is used for resource allocation, this weakness can cause too many (or too few) resources to be allocated, possibly enabling crashes if the product requests more resources than can be provided. If the calculated result involves time values, then the product might crash when it encounters a time that is less than the previously-calculated time.
Integrity
Technical Impact: Modify Memory
If the value in question is important to data (as opposed to flow), simple data corruption has occurred. Also, if the overflow/wraparound results in other conditions such as buffer overflows, further memory corruption may occur.
Confidentiality,Availability,Access Control
Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism
This weakness can sometimes trigger buffer overflows, which can be used to execute arbitrary code. This is usually outside the scope of the product's implicit security policy.
Availability,Other
Technical Impact: Alter Execution Logic; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU)
If the overflow/wraparound occurs in a loop index variable, this could cause the loop to terminate at the wrong time - too early, too late, or not at all (i.e., infinite loops). With too many iterations, some loops could consume too many resources such as memory, file handles, etc., possibly leading to a crash or other DoS.
Access Control
Technical Impact: Bypass Protection Mechanism
If integer values are used in security-critical decisions, such as calculating quotas or allocation limits, integer overflows can be used to cause an incorrect security decision.
Access Control
Technical Impact: Bypass Protection Mechanism; DoS: Crash, Exit, or Restart
If integer values are used in time-based, security-critical decisions, such as calculating expiration times or determining whether an event occurs within a specific time or date range, to cause an incorrect security decision. The consequences could even include "self-DoS" if the overflow produces a time value that is not accounted for in protection mechanism logic [REF-1570].
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